Cardiac performance and resistance to flow in vascular beds are subject to tonic and phasic activity of autonomic effectors. Afferent input from arterial baroreceptors are a major determinent of autonomic effector activity. Changes produced by various inputs other than the arterial baroreceptors, can be considered factors capable of influencing both the set point and the gain of the baroreceptor reflex. Resetting of the blood pressure control system is of key importance in integrated cardiovascular control. Present experimental evidence implicates a large neurogenic component in spontaneous hypertensive animal models as causal to resetting blood pressure control to higher levels. Brain stem and spinal cord neural mechanisms that participate in a cardiovascular state-change are important to autonomic hyperactivity and the subject of this study. The objective pursued to evaluate the neurogenic components leading to autonomic hyperactivity are: a) to characterize the behavior patterns of neurons in the vasomotor reticular network under control conditions and with stimuli which force a CV state-change, b) to correlate these patterns with that of preganglionic sympathetic elements in the lateral horn of the thoracic spinal cord, c) to assess the change in neuron response properties with intracisternal injections of central vasoactive drugs and d) to identify brain stem elements that respond in a paradigm of stimuli which force the CV state-change as part of the central adrenergic system. Our study attempts to understand what areas of the brain and how they interrelate to guide the action of the heart and blood vessels through ever changing conditions that man meets daily.